Abrasive materials and superhard materials, i.e., superabrasives such as natural and synthetic diamonds and cubic boron nitride, exhibit outstanding ability for machining both metallic and non-metallic materials. They are frequently used in saw blade and grinding tools as a cutting point to cut, grind, polish a variety of hard and abrasive materials. When abrasive or superabrasive particles reinforced metal or ceramic composites or polymer based composites are used to perform a task, such as cutting or grinding or polishing a highly abrasive workpiece, the particles in the composite take most of applied force due to their higher Young's modulus. The shear and tensile stress built along the interface between the particles and the matrix may be very significant. The superabrasive particles are often pulled out from the matrix due to weak interface bonding. Because most of abrasives/superabrasives have relatively smooth surfaces and are inert to most chemical substances, there is little mechanical or chemical bonding between the particles and the matrix.
Premature gross pull-out of only partially used abrasive particles (“grit”) is a major factor in grinding wheel wear in resin, vitreous or metal bonds. Retention of diamond particles in the matrix, such as metals, ceramic, and polymer, is poor. As an example, diamond saw blades may lose up to 40% of the abrasive particles in the matrix during one cutting use.
An approach for enhancing the adhesion of abrasive and superabrasive particles to the resin, vitreous, or metal bond, may utilize bond compositions which are reactive with the abrasive particles so that during tool fabrication the bond composition adheres to the surface of the abrasive particles. For example, U.S. Pat. Nos. 5,190,796 and 5,232,469, both herein incorporated by reference, teach methods to improve the retention of diamonds in abrasive tools by providing/coating the diamond particles with multiple layers of metals, such as molybdenum, titanium, niobium, chromium, zirconium, copper and nickel. As another example, U.S. patent application Ser. No. 09/901,159, herein incorporated by reference, discloses incorporating a silane coupling agent into a mixture of metal coated superabrasive particles and resin bond matrix to enhance the bond between the coating and the resin matrix.
In another approach to enhance or increase the retention of the grits in the matrix, the surface of the diamond particles is modified. For example, U.S. Pat. No. 3,650,714, herein incorporated by reference, proposes adding ceramic whiskers during the coating of diamond with copper or nickel and also obtaining roughness by heating a mixture of sponge iron and braze coated diamond under a vacuum. As another example, U.S. Pat. No. 4,435,189, herein incorporated by reference, discloses metal coated abrasives with a controlled, rough textured surface, for improved adherence to resinous materials. The controlled, rough textured surface is prepared by interrupting the electroless coating process to passivate diamond surface and then reactivate the passivated surface each time with a catalytic material to control the metal deposition rate for “rougher” grit.
There is a need for an improved method to enhance the bond strength between coated abrasive/superabrasive particles and the matrix as well as the bond strength between the abrasive/superabrasive crystals and its metal coating. A novel and inventive approach to enhance the retention of coated abrasive particles in a matrix through the interface design has been found.